Volume 29 Issue 1 - April 24, 2015 PDF
Nitrogen-Doped Graphene-Oxide Quantum Dots as Photocatalysts for Overall Water-Splitting under Visible Light Illumination
Te-Fu Yeh1, Chiao-Yi Teng1, Shean-Jen Chen2,3, Hsisheng Teng1,2,*
1 Department of Chemical Engineering, National Cheng Kung University
2 Center for Micro/Nano Science and Technology, National Cheng Kung University
3 Department of Engineering Science, National Cheng Kung University
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We have recently succeeded in producing nitrogen-doped graphene oxide quantum dots (NGO-QDs) with large surface area and optimized functionalization. Visible-light illumination of NGO-QDs in pure water resulted in evolution of H2 and O2 at a molar ratio of approximately 2:1. We hypothesize that the unique character of the NGO-QDs are caused by p- and n-domains in the material. The sp2 clusters in NGO-QDs can serve as the junction between the p- and n-domains and are the recombination sites for majority carriers from the two domains (Scheme 1). This photochemical diode-type mechanism for water splitting over NGO-QDs shows interesting analogies to that of biological photosynthesis and could provide a strategy to design semiconductor architectures on graphene to mimic the vectorial charge displacement in biological photosynthesis. The preliminary findings highlight the potential of NGO-QDs for water splitting achievable in a sustainable and environmentally-friendly manner. However, optimization of the material is required to compete with traditional photocatalysts in terms of yield and long term stability. We are still on the way to increase our fundamental understanding of the materials and design strategies for improving the efficiency.

Scheme 1 (Left) structure of nitrogen-doped graphene oxide quantum dots, NGO-QDs. (Right) p-n diode configuration of NGO-QDs for water splitting.
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